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rtc: hibvt: do not set the clock to 1970 from a counter that lost power #80

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Merged
openipc-ai merged 1 commit into from
Oct 20, 2026
Merged

rtc: hibvt: do not set the clock to 1970 from a counter that lost power #80

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38 changes: 27 additions & 11 deletions drivers/rtc/rtc-hibvt.c
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Original file line number Diff line number Diff line change
Expand Up @@ -117,6 +117,13 @@ union u_spi_rw {
#define REG_LOCK_STAT BIT(1)
#define REG_LOCK_BYPASS BIT(2)

/*
* A counter that lost every supply restarts from zero and reads as 1970.
* Times before 2000-01-01 are refused both ways, so such a counter reads
* as unset and every time set_time() accepts can be read back.
*/
#define RTC_MIN_VALID_SEC 946684800UL

#define RTC_RW_RETRY_CNT 5
#define SPI_RW_RETRY_CNT 500
#define RTC_SLEEP_TIME_MS 20
Expand Down Expand Up @@ -212,12 +219,15 @@ static int hibvt_rtc_read_time(struct device *dev, struct rtc_time *time)
return ret;
}

if (raw_value & LV_INT_MASK) {
//dev_err(dev,
// "low voltage detected, date/time is not reliable.\n");
(unsigned int)hibvt_spi_write(rtc->regs, RTC_INT_CLR, 1);
//return -EINVAL;
}
/*
* Not a verdict on the time: on a hi3516ev300 the flag stays set,
* and returns about half a second after each clear, with a fresh
* backup cell that keeps the counter through a power cut, exactly as
* it did with a flat one. The counter below is what tells. Clear the
* flag by its own bit: writing 1 acknowledged the alarm instead.
*/
if (raw_value & LV_INT_MASK)
hibvt_spi_write(rtc->regs, RTC_INT_CLR, LV_INT_MASK);

ret |= (unsigned int)hibvt_spi_rtc_read(rtc->regs, RTC_LORD, &raw_value);
if (raw_value & REG_LOCK_BYPASS)
Expand Down Expand Up @@ -251,6 +261,13 @@ static int hibvt_rtc_read_time(struct device *dev, struct rtc_time *time)
day = (dayl | (dayh << 8));
seconds = DATE_TO_SEC(day, hour, minute, second);

/*
* Report a counter that restarted from zero as unset, so hctosys
* leaves the clock alone instead of stepping it to 1970.
*/
if (seconds < RTC_MIN_VALID_SEC)
return -EINVAL;
Comment thread
qodo-free-for-open-source-projects[bot] marked this conversation as resolved.

rtc_time_to_tm(seconds, time);

return rtc_valid_tm(time);
Expand All @@ -268,6 +285,8 @@ static int hibvt_rtc_set_time(struct device *dev, struct rtc_time *time)
ret = rtc_tm_to_time(time, &seconds);
if (ret)
return ret;
if (seconds < RTC_MIN_VALID_SEC)
return -EINVAL;
days = SEC_TO_DAY(seconds);

ret |= (unsigned int)hibvt_spi_rtc_write(rtc->regs, RTC_LR_10MS, 0);
Expand Down Expand Up @@ -554,11 +573,8 @@ static int hibvt_rtc_init(struct hibvt_rtc *rtc)
return ret;
}

if (val & LV_INT_MASK) {
/* dev_err(&rtc->rtc_dev->dev,
"low voltage detected, date/time is not reliable.\n"); */
hibvt_spi_write(rtc->regs, RTC_INT_CLR, 1);
}
if (val & LV_INT_MASK)
hibvt_spi_write(rtc->regs, RTC_INT_CLR, LV_INT_MASK);

return ret;
}
Expand Down